1. Field of the Invention
The present invention relates to an object, a method, a manufacturing method, a process, a machine, a manufacture, or a composition of matter. In particular, the present invention relates to, for example, a semiconductor device, a display device, a light-emitting device, a driving method thereof, or a manufacturing method thereof.
In this specification, a semiconductor device means all types of devices that can function by utilizing semiconductor characteristics, and a transistor, a semiconductor circuit, a memory device, an imaging device, a display device, an electro-optical device, an electronic device, and the like are all semiconductor devices.
2. Description of the Related Art
A technique by which transistors are formed using semiconductor thin films has been attracting attention. The transistor is applied to a wide range of electronic devices such as an integrated circuit (IC) or an image display device. A silicon-based semiconductor material is widely known as a material for a semiconductor thin film applicable to a transistor. As another material, an oxide semiconductor has been attracting attention.
For example, a transistor using an amorphous oxide containing indium (In), gallium (Ga), and zinc (Zn) for a channel formation region of a transistor is disclosed (see Patent Document 1).
Further, it is known that oxygen is released from an oxide semiconductor in a manufacturing process, so that an oxygen vacancy is formed (see Patent Document 2).